Children&#39;s building block



FIG. 1 is a top plan view, the bottom being plain and unadorned;

FIG. 2 is a front elevation view thereof, showing the design. The back elevational view being identical to the front elevational view;

FIG. 3 is a right side elevational view thereof, showing the design. The left side elevational view being identical to the right side elevational view;

FIG. 4 is a sectional view showing the interior of two of the design; and,

FIG. 5 is a perspective view of the design. 

The ornamental design for a children's building block, as shown and described. 